The invention relates to jaw crushers as used in mines or in aggregate producing industries as a primary crusher.
Prior art jaw crushers can be classified into three types, namely single toggle jaw crushers, double toggle jaw crushers, and dodge jaw crushers. Dodge type jaw crushers have very little usage and single toggle jaw crushers are simple in construction and light weight so they have advantages in portable crushing plants. Double toggle jaw crushers are rugged and heavy, so they are usually used in big stationary crushing plants.
Although single toggle jaw crushers are simple in construction and light weight, the eccentric shafts and bearings are located in the upper parts of the crushers and are used to directly apply the significant forces needed to crush heavy aggregate. Particularly with hard materials to be crushed bearings wear is substantial and bearing life is short and as the orbit of a movable jaw is not linear, that is the orbit of the upper part of movable jaw describes a circle and the lower part of a movable jaw describes an elliptical or upwardly slanting line, the wear rate of a jaw liner is high particularly as compared to that of a double toggle jaw crusher. A type of single toggle jaw crusher of the prior art is shown in FIG. 30.
A double toggle jaw crusher has a movable jaw suspended by a large bushing and pin assembly with the movable jaw driven back and forth by a double toggle. The double toggle is connected to a pitman that is powered by an eccentric shaft. In a double toggle jaw crusher, the force required to crush aggregate like large stones is primarily exerted by the bushing pin assembly. As the double toggle acts as a force magnifying device, the force that is exerted on the bearings of the eccentric shaft is small compared to that of a single toggle jaw crusher, generally ⅕ or ⅙ of the force. As a result, the life of the bearings are much longer in a double toggle jaw crusher as compared to the prior art single toggle jaw crushers. In addition, the life of the jaw liners of a double toggle jaw crusher are much longer due to linear movement of the movable jaw.
However, a double toggle jaw crusher is much larger than a single toggle jaw crusher due to the long double toggle and the orientation of the size adjusting mechanism for adjusting the size of crushed stones exiting the crushing chamber. This requires the construction of larger and heavier double toggle jaw crushers which are more costly than a single toggle jaw crusher of equivalent capacity. As a consequence, there is a need for a jaw crusher that has the size, weight and simplicity of construction advantages of single toggle jaw crushers with the durability of a double toggle jaw crusher.